Process for polymerization of tetrahydrofuran

ABSTRACT

Tetrahydrofuran is polymerized in the presence of a catalyst system of 5-50 percent by weight of fuming sulfuric acid, based on the weight of tetrahydrofuran, and 0.008-90 percent by weight of a metal belonging to Group V or VI in the Periodic Table, based on the free SO3 content in the fuming sulfuric acid.

Elite Sees me 1 Matsuda et al.

M IMarch 13, 1973 [75] Inventors: Kazuo I 1 PROCESS FOR POLYMERIZATION OF TETRAI'IYDROFURAN Matsuda, Wakayama;

Yoshiaki Tanaka, Osaka; Takeyo Sakai, Wakayama, all of Japan [73] Assignee: Kao Soap (30., Ltd., Chuo-ku,

Tokyo, Japan [22] Filed: Sept. 13,1971

[21] Appl. No.: 180,175

[30] Foreign Application Priority Data Sept. 16, 1970 Japan ..45/81008 [52] [1.8. CI. ..260/615 B [51] Int. Cl. ..C07c 41/00, C07c 43/00 [58] Field of Search ..260/615 B [56] References Cited UNITED STATES PATENTS 3,454,652 7/1969 Dunlop et al. ..260/615 B 2,856,370 10/1958 Muetterties ..260/615 B 3,359,332 12/1967 Johnston 1 260/615 B 3,487,l l5 l2/l967 Lovell t ..260/615 B 2,751,419 6/1956 Hill et al. ..260/615 B FOREIGN PATENTS OR APPLICATIONS 766,208 6/1953 Germany ..260/615 Primary Examiner-Howard T. Mars Att0rneyW0odhams, Blanchard and Flynn [57] ABSTRACT Tetrahydrofuran is polymerized in the presence of a catalyst system of 5-60 percent by weight of fuming sulfuric acid, based on the weight of tetrahydrofuran, and 0008-90 percent by weight of a metal belonging to Group V or VI in the Periodic Table, based on the free SO content in the fuming sulfuric acid.

7 Claims, No Drawings PROCESS FDR PQLYMERIZATION F TETRAHYDRQFURAN BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a process for polymerization of tetrahydrofuran, and more particularly, it relates to a process for the ring-opening-polymerization of tetrahydrofuran in the presence of a novel improved catalyst.

2. Description of the Prior Art Ordinarily, tetrahydrofuran is subjected to ringopening-cationic polymerization in the presence of a Lewis acid catalyst and some of the protonic acids, and there are produced various polymers ranging in state from liquid to solid, depending on the degree of polymerization. it is, however, necessary to stop the polymerization by adding water and then hydrolyzing the chlorine atoms or acetylester groups at the terminals of the polymer to convert completely to hydroxyl groups for obtaining a polymer having diols at both ends. For this process, severe reaction conditions are required, and the process becomes more complicated, resulting in an increased loss of the polymer. There are also some catalysts which are corrosive to the materials of apparatus, such as fluoro-sulfonic acid.

We have proposed a process using fuming sulfuric acid (Japanese Patent application No. 15932/1969, corresponding to US. Ser. No. 13 839) for overcoming these defects. By this latter process a polymer ofa good quality can be produced very economically, but polymers having an average molecular weight higher than 1,200 are difficult to obtain, and it is also difficult to control their molecular weight.

We have extensively investigated in order to solve these difficult problems, and discovered that the degree of polymerization and the molecular weight can be increased by causing a small amount of a metallic sub stance to coexist with fuming sulfuric acid in a given range of concentration and that the molecular weight of the produced polymer can be optionally controlled by changing the amount of catalyst of a given composition added to the system.

SUMMARY OF THE INVENTKON This invention provides a process for polymerizing tetrahydrofuran in the presence of fuming sulfuric acid having a free S0,, content in the range of from about 15 percent by weight to about 43 percent by weight and additionally containing about 0.008 to 90 percent by weight ofa metal compound belonging to Group V and VI in the Periodic Table, based on the weight of free SO, in the fuming sulfuric acid.

When the free SO content of the fuming sulfuric acid exceeds 43 percent by weight, the polymer begins to be carbonized, and also the polymer is colored so much that it is hard to decolor by post-treatment. When the free $0 content of the fuming sulfuric acid is lower than 15 percent by weight, the yield of the polymerization cannot be increased even if the abovedescribed co-catalyst is used. There is usually employed fuming sulfuric acid containing 23-28 percent by weight of free 80;, which is readily available commercially.

The co-catalyst to be used, together with fuming sulfuric acid, is a compound such as an oxide or oxygen acid of a metal belonging to Group V or VI in the Periodic Table, such as vanadium, niobium, chromium, and molybdenum. About 0.008 to about 90 percent by weight of the co-catalyst compound is used, based on the weight of the free S0 in the fuming sulfuric acid.

The amount of fuming sulfuric acid catalyst used is in the range of 5-50 percent by weight based on the weight of tetrahydrofuran.

The polymerization reaction can be carried out in the presence or absence of a solvent. It is preferable to use a polymerization solvent only when it is necessitated, because it usually causes a reduction of the rate of polymerization. As solvents, there may be exemplified aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers and other substances that do not affect adversely the polymerization reaction. There is no limit as to the amount of the solvent to be used.

The polymerization reaction may be performed either in a nitrogen atmosphere or in air, provided that the reaction is kept free from moisture. The polymerization temperature is in the range of from -40 to C., preferably from 20 to 10C.

According to the process of this invention, the rate of polymerization and the molecular weight can be increased, compared with the process using only fuming sulfuric acid, and the molecular weight of the polymer can be controlled at will.

The molecular weight of the polymer can be controlled by varying the amount of the catalyst compared to the weight of tetrahydrofuran, keeping the ratio of fuming sulfuric acid to the metal co-catalyst compound constant. If the amount of the catalyst is reduced, both of the molecular weight and the rate of polymerization increases.

Some illustrative, nonlimiting examples of this invention are set forth hereinafter. in the examples, all parts and percentages are by weight, unless otherwise noted.

EXAMPLE 1 One hundred parts of tetrahydrofuran were placed in a 500 ml. four-mouthed flask provided with an agitator, a thermometer, a condenser, and a dropping funnel; the vessel was externally cooled and a nitrogen atmosphere was maintained therein. Tetrahydrofuran was agitated sufficiently, and the temperature in the system was maintained at 5 to 0C. while a given amount of a catalyst composition, prepared by dissolving a given amount of chromium trioxide in fuming sulfuric acid at a room temperature or an elevated temperature, was added in drops into the polymerization system. The reaction was exothermic but the materials were sufficiently agitated and cooled so as to maintain the temperature no higher than 0C. After the end of the catalyst addition, agitation was continued further for 2 hours at a temperature of from 5 to 0C. Then, 200 parts of water were added to stop the polymerization. A dehydration tube was attached to a reflux condenser; the reaction product was heated on a water bath with agitation, and the unreacted monomer was collected through the dehydration tube. The product was further agitated for 2 hours with heating at -100 C. to hydrolyze the terminals of the polymer. The product was allowed to cool, and it separated into 2 layers. The upper layer was collected, neutralized,

28% fuming sulfuric acid (g) 16 21 34 Amount of CIO; (g) 1.18 1.54 2.5

Yield based on monomer (96) 70.8 71.6 60.8 Average molecular weight calculated from the terminal OH groups 4291 3120 1556 Control 1 Tetrahydrofuran was polymerized with a catalyst of only fuming sulfuric acid by a process similar to the one described in Example 1, and the results shown in Table 2 were obtained.

Table 2: Relations between the amount of catalyst and the yield and the molecular weight of the produced polymer Amount of 28% fuming sulfuric acid (g) 15 21 34 Yield based on monomer 26 42.5 59.5 Average molecular weight calculated from the terminal OH groups 1007 1020 760 As clearly seen in Tables 1 and 2, it is difficult to make the molecular weight higher than 1,000 using only fuming sulfuric acid as a catalyst, but when there is additionally present a small amount of chromium trioxide, the molecular weight can be varied regularly by varying the amount of catalyst, and thus there can be produced a polymer having the molecular weight higher than 1,000.

EXAMPLE 2 polymer Weight ratio of 28% fuming sulfuric acid/vanadium pentoxide 8.5 (constant) 28% fuming sulfuric acid (g) 16 26 34 Amount of V,O, (g) 1.88 3.06 4

Yield based on monomer 71.8 71.6 60.8 Average molecular weight calculated from the terminal OH groups 3077 1549 990 EXAMPLE 3 According to the process described in Example 1, 100 parts of tetrahydrofuran were polymerized in the presence of a catalyst consisting of 43 percent fuming sulfuric acid molybdenum trioxide composition, and a refined polyether glycol was obtained.

The results are shown in Table 4.

Table 4: Relations between the amount of catalyst and the molecular weight and the yield of the produced polymer Weight ratio of 43% fuming sulfuric acid/M00 15.4 (constant) 43% fuming sulfuric acid (g) 15 22 34 M00. (g) 0.98 1.44 2.22

Yield based on monomer 64.2 63.3 53.8 Average molecular weight calculated from the terminal OH groups 1711 1160 787 EXAMPLE 4 According to the process described in Example 1, 100 parts of tetrahydrofuran were polymerized in the presence of a catalyst consisting of 23 percent fuming sulfuric acid barium chromate composition, and a refined polyether glycol was obtained.

The results are shown in Table 5.

Table 5: Relations between the amount of catalyst and the molecular weight and the yield of the produced polymer Weight ratio of 23% fuming sulfuric acid/BaCrO 16.8 (constant) 23% fuming sulfuric acid (g) 16 21 34 BaCrO (g) 0.95 1.25 2.02

Yield based on monomer 67.0 65.9 53.4 Average molecular weight calculated from the tenninal OH groups 3530 2730 1440 The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the polymerization of tetrahydrofuran, which comprises polymerizing tetrahydrofuran in the absence of water and in the presence of (a) from 5 to 50 percent by weight, based on the weight of tetrahydrofuran, of fuming sulfuric acid having a free SO content of about 15 43 percent by weight and (b) a metal compound selected from the group consisting of barium chromate and oxides of chromium, vanadium, niobium and molybdenum in an amount in the range of 0.008 90 percent by weight based on the free S0 content in the fuming sulfuric acid, at a polymerization temperature in the range of -40 to +C. and then hydrolyzing the terminal group of the polymer.

2. The process as claimed in claim 1, wherein the free 80;, content of said fuming sulfuric acid is in the range of from 23 percent by weight to 28 percent by weight.

3. The process as claimed in claim 1, wherein the polymerization reaction is carried out in the absence of a solvent.

polymerization system at 90 100C. to hydrolyze the polymer, cooling the polymerization system so as to separate the polymer having terminal hydroxyl groups at both ends of the molecule as an upper oil layer, sub- 5 jecting the upper oil layer to neutralization, dehydration and desalting steps to obtain the purified polymer.

7. A process as claimed in claim 1, in which the metal in the polymerization system is added in the form of a compound selected from the group consisting of chromium trioxide, vanadium pentoxide, molybdenum trioxide and barium chromate. 

1. A process for the polymerization of tetrahydrofuran, which comprises polymerizing tetrahydrofuran in the absence of water and in the presence of (a) from 5 to 50 percent by weight, based on the weight of tetrahydrofuran, of fuming sulfuric acid having a free SO3 content of about 15 - 43 percent by weight and (b) a metal compound selected from the group consisting of barium chromate and oxides of chromium, vanadium, niobium and molybdenum in an amount in the range of 0.008 - 90 percent by weight based on the free SO3 content in the fuming sulfuric acid, at a polymerization temperature in the range of -40* to +80*C. and then hydrolyzing the terminal group of the polymer.
 2. The process as claimed in claim 1, wherein the free SO3 content of said fuming sulfuric acid is in the range of from 23 percent by weight to 28 percent by weight.
 3. The process as claimed in claim 1, wherein the polymerization reaction is carried out in the absence of a solvent.
 4. The process as claimed in claim 1, wherein the polymerization reaction is carried out in the presence of a solvent selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons and ethers.
 5. The process as claimed in claim 1, wherein the reaction temperature is in the range of about -20* to about 10*C.
 6. The process as claimed in claim 1, wherein the polymerization is stopped by the addition of water, then heating the polymerization system to recover nonreacted tetrahydrofuran, further heating the polymerization system at 90* - 100*C. to hydrolyze the polymer, cooling the polymerization system so as to separate the polymer having terminal hydroxyl groups at both ends of the molecule as an upper oil layer, subjecting the upper oil layer to neutralization, dehydration and desalting steps to obtain the purified polymer. 